Neither of our Chem-Dip products is a great solution for a one-time cleaning.  Your best bet for dissolving carbon from EGR and PCV valves is to use Berryman B-12 Chemtool Carburetor, Choke & Throttle Body Cleaner aerosol (part #0117 & part #0120).  If you want a soak-type product, you can use Berryman B-12 Chemtool Fuel Injector Cleaner (part #0116).  If soaking, avoid exposure to excessive heat, sparks, and flames, and make sure you soak in something chemical resistant (glass or metal, for example) with a lid to prevent evaporation.